A mayoralty candidate's campaign signs and headquarters were the target of vandals overnight.

Around 20 of Naheed Nenshi's signs were tampered with or destroyed in northwest Calgary, causing hundreds of dollars in damage.

A concrete block was also thrown through the window of Nenshi's campaign office located at 615 16 Avenue N.E.

Chima Nkendirim, Nenshi's campaign director, says the attack coincided with the anniversary of 9-11 and a spate of anti-Muslim attacks against Nenshi on the Internet.

"It is sad that people have to draw such negative stereotypes. These comments are so outdated and clearly do not represent the feelings of the vast majority of Calgarians," said Nkendirim.

Nenshi's signs have been vandalized before. Nkendirim says the difference between the previous incidents and this one is the organized nature and scope of the attack.

"Our campaign team was able to provide a description of the people attacking these signs to Calgary police. We hope the public will be able to provide additional information to police through Crime Stoppers. This type of vandalism directed towards any minority group has got to stop."

Anyone with information is asked to call the Calgary Police Service at 403-266-1234 or Crime Stoppers at 1-800-222-TIPS (8477).